Seymour Narrows was described by Captain George Vancouver as "one of the vilest stretches of water in the world." Even after Ripple Rock was removed, it remains a challenging route. In March 1981, the Star Philippine, a freighter, ran aground in the narrows.
Seymour Narrows is notable also because the flowing current can be sufficiently turbulent to realize a Reynolds number of about , i.e. one billion, which is possibly the largest Reynolds number regularly attained in natural water channels on Earth. Turbulence develops usually around a Reynolds number of 2000, depending on the geometric structure of the channel.
Ripple Rock was a submerged twin-peak mountain that lay just nine feet beneath the surface of Seymour Narrows. It was a serious hazard to shipping, sinking 119 vessels and taking 114 lives. The gunboat USS Saranac was one of the rock's first recorded victims. On April 5, 1958, after twenty-seven months of tunnelling and engineering work, Ripple Rock was blown up with 1,375 tons of Nitramex 2H explosive making it the largest commercial, non-nuclear blast in North America. The Halifax Explosion in 1917 was larger but it was not a deliberate act.
The event was broadcast live on Canadian Television. The footage is also regularly screened at the Campbell River Museum.
Vancouver band The Evaporators wrote a song about the event and released it on their 2004 album Ripple Rock.
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